1. Field of the Invention
The present invention relates to a backlight scene judging method for judging whether a scene, which is taken by a digital camera or a scanner having a color solidstate image pickup device, is backlighted or not.
2. Description of the Prior Art
In a backlight scene, a very bright portion such as a light source generally exists behind a main object, and the main object is shaded. When an exposure of a camera is automatically controlled under the backlight scene, a luminance sensor such as an exposure meter or a solidstate image pickup device is affected by a luminance of the bright portion. Thus, a portion of a film or the solidstate image pickup device corresponding to the main object is insufficiently exposed.
Conventionally, it is proposed that the backlight scene is automatically sensed by the camera and an exposure condition based on an output of the luminance sensor is compensated. For example, a picture frame of the image pickup device is divided into a plurality of regions, and a luminance is sensed with respect to each region. A ratio of a number of dark regions having values of the luminance smaller than a threshold value to a number of bright regions having values of the luminance equal to or larger than the threshold value is obtained. The camera judges whether the scene is backlight or not by corresponding to the ratio.
However, when a dark portion except the main object exists in the picture field, the above-mentioned ratio becomes larger. As a result, the camera erroneously judges the scene is backlighted even though it is not backlighted.